Indicating cigarette filter



Feb. 27, 1968 F J sHU. Tz ETAL 3,370,592

INDICATING CIGARETTE FILTER Filed Nov. 12, 1965 PAPER WRAPPED TRANSPARENT FILM WRAPPED (HEAT SEALED) TRANSPARENT FILM INVENTORS: FREDERICK J. SCHULTZ CLIFFORD O. JENSEN ALBERT B. HUDSON THEIR ATTORNEYS United States Patent 3,370,592 INDICATING CiGARETTE FILTER Frederick J. Schultz, Clifford 0. Jensen, and Albert B. Hudson, Greensboro, N.C., assignors to P. Lorillard Company, New York, N.Y., a corporation of New Jersey Filed Nov. 12, 1965, Ser. No. 507,353 16 Claims. (Cl. 131-103) This invention relates to smoking tobacco products, particularly to improvements in filters and filter tips for cigarettes.

Filters in cigarette and cigar holders and filter tips for cigarettes have been used for many years, and, in recent years, their use has become widespread for the reason that they are recognized as having the capability of removing tars and other condensable components of tobacco smoke thought to be harmful. Reagents and absorbents of various kinds have been included in such filters to remove other components from the tobacco smoke while enabling the flavor and aroma-containing components of the smoke to pass through the filters. None of these filters or filter tips indicates the amount of the unwanted components which are removed from the smoke except for a brownish, tarry appearing discoloration at the end of the filter tip or in the filter, if used in a cigar or cigarette holder. Accordingly, the smoker is not informed as to the condition of the filter in the cigarette and particularly whether the filter is removing unwanted components.

In accordance with the present invention, filters for cigarette and cigar holders, and particularly filter tips for ci arettes, little cigars, cigarillos and the like are provided with readily visible means for indicating, by a change of color, the absorption of unwanted components, such as, for example, aldehydic, acidic or basic (alkaline) components, by the filter medium.

More particularly, in accordance with the invention, filter tips for cigarettes are provided with an absorptive and filtering medium visible through a Window or opening in the filter tip and impregnated with an indicator which changes color when the filter has absorbed a significant amount of such components as the aldehydic or acidic components of tobacco smoke, In addition, the filter medium may be treated with a reagent which changes or converts the unwanted component to a harmless component and after the added reagent has been utilized, a

visible indication theerof is given by the change in color of the filter medium in the filter tip.

In accordance with the invention, at least a portion of the filter medium in the filter tip may be treated with a carbonyl-sensitive indicator, such as, for example, the triphenylmethane dyes, which are useful for indicating the presence of aldehydes, or an acid-base indicator, which indicates an acidic or basic state. Moreover, the filter medium carrying the indicator may be impregnated with a reagent, such as, for example, sodium bisulfite, which converts aldehydes to non-volatile compounds, or with a mild base, such as sodium bicarbonate, which reacts with the acidic components and removes a part of them from the cigarette smoke. In this way, the new filter tip embodying the present invention not only is capable of removing condensable components, but also indicating when a sizable concentration of unwanted components have reacted in the filter medium.

For a better understanding of the present invention, reference may be had to the accompanying drawings, in which:

FIGURE 1 is a schematic illustration of the preparation of a filter tip of the kind embodying the present invention for a cigarette; and

FIGURE 2 is a perspective view of a completed cigarette having the filter tip attached thereto.

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In the preparation of a single or dual filter tips for cigarettes, it is usual to provide the filtering medium in the form of rods having a paper Wrapping thereon, the rods being equal in length to a plurality of filters or filter sections, for example, six such filters or filter sections. The rods are cut into appropriate lengths and separated into rows by means of known machines, such as, for example, the machine shown in the Brown et al. Patent No. 3,165,953 dated Jan. 19, 1965, and then attached to the ends of cigarettes and secured thereon with a Wrapping of tipping paper.

In accordance with the present invention, and as shown schematically in FIGURE 1 of the drawing, a filter rod 16, which may be suitably composed of a mass 11 of fibers, such as alpha cellulose fibers, mixtures of mineral and cellulosic fibers, and the like, and with a paper wrapping 12 thereon, is supplied in lengths corresponding with a plurality of filter sections or plugs. As illustrated, the rod 10 is equal to three sections or plugs for a dual filter, although its length may correspond to six or any other desired number. A plug 13 of the paper wrapped filter material is to be assembled with a plug 14 of another filter material cut from a rod 15 which has a wrapping of transparent material 16, such as cellophane or the like, enclosing the filter material 17. The filter material 17 may be suitably formed of crimped, absorbent crepe-like paper of the type commonly used in cigarette filters and which is quite porous and fragile and, when compressed or rolled into a rod-like form, is porous and absorbent. This paper is impregnated with a suitable indicator which changes color in the presence of a predetermined concentration of an unwanted component of tobacco smoke. Thus, for example, the paper rod maybe impregnated with an indicator in the manner disclosed in the following examples.

Example I.A solution of 0.4 gm. of malachite green oxalate in 500 ml. of water is adjusted to a pH of 3 by the addition of oxalic acid. The solution is then decolorized by adding 15 gms. of sodium bisulfite and stirring for 30 minutes. The resulting precipitate is removed by filtration and discarded. Two hundred fifty ml. of propylene glycol are added along with 5 grns. of the tetra sodium salt of ethylenediamine tetraacetic acid. The solution is then made to final volume by the addition of 250 ml. of water and the pH is adjusted to 7.2 by the addition of approximately 5 grns. of sodium carbonate.

This solution is applied to the paper during the filter rod manufacturing process by means of a spray which applies approximately 58 milligrams per 10 mm. filter section. The resulting filters are white or very pale green. On contact and reaction with aldehydes in the smoke, the filter changes from white to bright green, thus indicating the removal from the smoke of aldehydes.

Example II.Pararosaniline acetate can be substituted for malachite green oxalate in Example I. The result is a pale pink filter section which on contact and reaction with the aldehydes in cigarette smoke turns to a reddish purple color.

Example lII.Rosaniline acetate can be substituted for pararosaniline acetate in Example II with similar results.

Formulations very similar to these cited in the above examples can be used with other salts of the triphenylmethane dyes mentioned, that is, one may use malachite green hydrochloride or malachite green acetate rather than the oxalate salt used in the illustration. In like manner, one may use various salts of pararosaniline or rosaniline with similar final results.

It is also possible to use other members of'the triphenylmethane dye family, such as methyl violet, crystal violet, acid fuchsin, and the like, with minor variations in the above-described formulation, thus allowing one to arrive particular dye chosen. The sodium bisulfite present in the indicator reacts with aldehydes and converts them to non-volatile compounds.

Another group of compounds suitable for use as color change reagents in cigarette filters is that group generally known as acid-base indicators. These are compounds of a variety of chemical classes whose color depends upon the acidity or basicity of the medium in which they find themselves. For example, litmus in an acid medium is pink, whereas in analkaline medium it is blue.

Experience has shown that all acid-base indicators can be used, when properly prepared, to give a color change on the filter when it comes in contact with cigarette smoke. Many of these indicators are not preferred, however, because of the dullness or lack of intensity of their colors or because their color changes do not cover a wide enough range of the spectrum, that is, a color change from blue to purple or from red to orange is not enough of a change for this purpose.

Some members of the acid-base indicator group of compounds, do, however, have brilliant colors and give good distinct color changes. The color change of each of these compoundsoccurs in a certain pH range or at a certain degree of acidity o'r basicity. Thus the pH range is a characteristic of the particular compound and the compounds available cover the entire range from strongly acidic (low pH) to strongly basic (high pH).- In addition to the use of these materials individually, they may be used in various combinations with one another as a means of arriving at the desired initial and final colors and/or as a means of having the color change take place in the desired pH range. Cigarette smoke contains both acids and bases, and the overall pH is about 5. If the indicating filter is poised at a low pH, then the smoke is alkaline with respect to this filter. On the other hand, if an indicating filter is poised at a high pH, the cigarette smoke is acid with respect to this filter. Thus, by appropriate choice of indicators and by adjusting the acidity or alkalinity of the filter, either an acid or a base type reaction can be obtained.

The following examples will serve to illustrate the use of various indicators which change at high, low, and medium or neutral pH ranges as well as the use of mixed indicators.

Example lV.-A solution of 2 gms. of 1-(2,4dinitrophe'nylaz'o)-2-naphthol-4-sulfonic acid sodium salt in 500 ml. of water is adjusted to a pH of 11.1 by the addition of approximately 12.5 gms. of sodium bicarbonate. This solution is sprayed onto creped paper filter material during the filter rod making process. The rods thus formed are combined with cellulose acetate fiber filter rods and attached to cigarettes as described hereinafter. On smoking of the cigarette, the paper filter section changes color from blue to yellow due to the absorption and reaction of acidic material from the smoke.

Example V.Two grams of brilliant yellow dissolved in 500 ml. of a saturated solution of sodium bicarbonate and followed by the addition of 500 ml. of ethylene glycol gives a reagent which when applied as noted in Example 1V produces a color change from bright red to yellow. This change occurs in the pH range 7.9-6.6 which requires that a rather large amount of sodium bicarbonate must have been reacted with acidic materials in the smoke 'be fore the initial pH of about 12 could be lowered to the color change range. Analytical data on the smoke from cigarettes having sodium bicarbonate in their filters does, in fact, show a marked reduction in the amounts of the volatile acids in the smoke.

Example VI.-A solution of bromocresol green (50 mg./5O ml. of water) containing 15 ml. of ethylene glycol and enough citric acid to lower its pH to 3.0 can be applied to a filter section as stated above to give a product which on smoking changes from yellow to green due to 4 I t the basic components of the smoke raising the pH of the filter to a value above 5.4.

Example Vl[.-An indicator mixture consisting of 10 mg. methylene blue in 30 ml. of ethanol combined with 30 mg. of phenol red dissolved in 20 ml. of water and 14 ml. of ethylene glycol is made basic by'the addition of 15 ml. of a water solution of sodium bicarbonate (5 ing/ml). When this reagent is incorporated intoa cigarette filter as stated above, the resulting filter changes from purple to green during smoking. This change occurs when the filter has absorbed enough acids to lower its pH to approximately 7.5. V

When anacid-base indicator is used, sodium bicarbonate, when present, neutralizes acidic components of tobacco smoke. The initial color of the filter material will remain until the sodium bicarbonate has been neutralized by the acidic components, whereupon the filter material changes color.

In making the dual filter, the plugs .13 and 14 are brought into end-to-end relation, and both of them are wrapped with a transparent film 18, such as, for example, transparent cellophane or other transparent plastic material which may be heat-sealed to retain the plugs 13 and 14 together. With such a transparent wrapping, the filling 17 in the plug 14 is visible while the filling 11 in the plug 13 is concealed, except at its end, by the paper wrapping 12 therearound. The dual filter is then attached to the end of a cigarette 19 by means of tipping paper 20, in the usual way, with the exception that the paper is provided with an opening 21 which overlies the filter plug 14 so that the filling or filtering material 17 therein is visible through the overlapping layers of transparent material 16 and 18. The completed filter as shown in FIG- URE 2 accordingly includes a window or opening 21 in the dual filter tip 22 afiixed to one end of the cigarette 19.

When the cigarette is smoked, the smoke travels first through the filter section 14 and components in the smoke are absorbed by this filter plug. Additional components are removed by the filter plug section 13 which generally has a more efiiective filtering action on the tarry and large particulate components of the smoke because its fibrous filler provides a multiplicity of extremely small and labyrinthine passages therethrough. The amount of aldehydic acidic or basic components can, of course, be reduced in the smoke by the inclusion of reagents of the type referred to above which further delay the color change of the indicator. In this way, the cigarette filter gives a clear and visible indication to the smoker of the effective.

ness of the filter in its action. I

It will be understood that other types of indicators than those referred to herein maybe included in the visible.

portion of the filter and that other reagents may be included in the filter to reduce the amount of unwanted components in the tobacco smoke. Also, it will be understood that instead of forming the filler of the indicating plug of the filter of crimped crepe paper, it may be formed of other fibrous material, although the crepe paper is preferred because of its ability to absorb and retain the indicator and other reagents as compared with other fibers which cannot be impregnated as readily with the indicators.

Accordingly, the form of the invention described herein should be considered as illustrative and not as limiting the scope of the invention as defined in the following claims.

We claim:

1. A filter for tobacco products comprising a plug of porous absorbent material containing an indicator additive incorporated therein which changes color in the presence of a significant amount of a selected component of tobacco smoke, a transparent wrapper around said plug and a wrapper of substantially opaque paper overlying said transparent wrapper and having an opening therein for viewing said plug and the change of color thereof.

2. A dual filter for cigarettes and the like comprising a first plug of porou absorbent material containing an indicator additive incorporated therein which changes color in the presence of a significant concentration of a selected component of tobacco smoke, a second plug of porous filtering material in end-to-end engagement with said first plug, a transparent wrapping enclosing said plugs and a paper wrapping overlying said transparent wrapping and having an opening therein overlying and exposing a portion of said first plug to view.

3. The filter set forth in claim 2 in which said material of said first plug is crepe smoke filter paper and said filtering material of said second plug is a mass of fibers.

4. The filter set forth in claim 2 in which said indicator is a carbonyl-sensitive indicator which changes color in the presence of aldehydes.

5. The filter set forth in claim 4 in which said indicator is malachite green.

6. The filter set forth in claim 4 in which said first plug contains sodium bisulfite for reaction with said aldehydes.

7. The filter set forth in claim 2 in which said indicator is an acid base indicator which changes color in the presence of acids and bases.

8. The filter set forth in claim 7 in which said first plug contains a weak base.

9. The filter set forth in claim 7 in which said first plug contains sodium bicarbonate.

10. The filter set forth in claim 2 in which said paper wrapping attaches the filter to a cigarette.

11. A method of making and attaching a filter tip to a cigarette and the like comprising assembling a first plug of porous filtering material in end-to-end relation to a second plug of porous filtering material containing an indicator which changes color in the presence of a significant concentration of a component of tobacco smoke, both of said plugs having wrappings confining said filtering material, the Wrapping of said second plug being transparent, wrapping both of said plugs in a transparent Wrapper and attaching said wrapped plugs to the end of a cigarette with tipping paper containing an opening overlying said second plug to expose a portion thereof to view.

12. The method set forth in claim 11 in which said indicator is an additive incorporated in the filtering material of said second plug and changes color in the presence of aldehydes.

13. The method set forth in claim 12 in which said second plug contains a compound reactive with aldehydes.

14. The method set forth in claim 11 in which said indicator is malachite green.

15. The method set forth in claim 11 in which said indicator is an acid-base indicator which change color in the presence of an acid.

16. The method set forth in claim 15 in which said second plug contains a material reactive with acids.

References Cited UNITED STATES PATENTS 2,815,760 12/1957 Schreus et al.

3,194,246 7/ 1965 Mantchev 13 l -263 X FOREIGN PATENTS 641,687 1/1937 Germany.

SAMUEL KOREN, Primary Examiner.

D. J. DONOHUE, Assistant Examiner; 

1. A FILTER FOR TOBACCO PRODUCTS COMPRISING A PLUG OF POROUS ABSORBENT MATERIAL CONTAINING AN INDICATOR ADDITIVE INCORPORATED THEREIN WHICH CHANGES COLOR IN THE PRESENCE OF A SIGNIFICANT AMOUNT OF A SELECTED COMPONENT OF TOBACCO SMOKE, A TRANSPARENT WRAPPER AROUND SAID PLUG AND A WRAPPER OF SUBSTANTIALLY OPAQUE PAPER OVERLYING SAID TRANSPARENT WRAPPER AND HAVING AN OPENING THEREIN FOR VIEWING SAID PLUG AND THE CHANGE OF COLOR THEREOF. 